Synthetic resin plastic compositions



Patented June 15, 1943 SYNTHETIC RESIN PLASTIC COMPOSITIONS Edgar C.Britton and Gerald H. Coleman, Midland, Mich., Company, Midland,Michigan as'signors to The Dow Chemical Micha corporation of No Drawing.Application March 15, 1941, Serial No. 383,552

4 Claims.

This invention concerns certain new plastic compositions comprising abenzene-insoluble glass-like resin derived from styrene and, as aplasticizing agent therefor, an ester oi levulinic acid.

It is known that solid resinous products may be obtained by polymerizingmonomeric styrene together with a variety of otherunsaturated organiccompounds containing oleflnic linkages, such as allyl cinnamate, diallylmalleate, and dioxylene dicinnamate. These and other typical examples ofsuch resinous products are described in the following United Statespatents: 2,047,398 to Voss et al..; 2,089,444 to Staudinger et al.;2,186,359 to Britton et al.; 2,186,360 to Britton et a1.; and 2,205,390to Britton et a1. Others are described in the co-pending applications ofBritton et 8.1.; Serial No. 199,892, filed April 4, 1938, and Serial No.324,230, filed March 15, 1940. These products are obtained as glass-likethermoplastic resins -or as opaque, white, friable materials.

Certain of thepolymers initially obtained as glass-like resins areinsoluble in benzene and other of the usual solvents or polystyrene, e.g. carbon tetrachloride, dioxane, methylene chloride, toluene, ethylbenzene, etc. In some cases the polymers are capable of being swelled insuch solvents to form insoluble gels. All such solid resinous productsare herein referred to as copolymers, although their exact chemicalconstitution is not definitely known. Similarly, the unsaturatedcompounds which may be employed in preparing such products are referredto as co-polymerizing agents and the polymerization of mixtures ofstyrene and such agents is referred to as co-polymerization." All ofsuch co-polymers of styrene possess properties which render themvaluable in the manufacture of molded or shaped objects, since they arestable to discoloration, have good dielectric strength, high mechanicalstrength and impermeability to moisture, and are resistant to attack byacids, aihalies, etc. In preparing such molded or shaped products,however, dificulty is encountered in securing adequate flow duringmolding without resorting to the use of molding temperaturesconsiderably higher than those usually employed in molding thermoplasticmaterials. Particular dimculty has been experienced with thebenzene-insoluble glass-like co-polymers since many of the compoundsemployed as plasticizing agents to increase the plasticity and flowduring molding or pure polystyrene or of soluble co-poiymers of styreneare unsatisfactory as plasticizing .plasticized with relatively agentsfor the insoluble co-polymers of styrene. Many of these plasticizersimpart the desired properties of the benzene-insoluble co-polymers onlywhen used in such large proportions that the mechanical strength of thecomposition is greatly reduced. Certain of such plasticizing agents arefurther disadvantageous in that they are not sufliciently compatible andtend to exude to the surface of the plasticized composition withresultant loss in plasticizing action and, frequently, blushing of thefinished product.

We have now found that esters of levulinic acid may be advantageouslyemployed as plasticizing agents or the benzene-insoluble glass-like 00-,

polymers of styrene. Compositions comprising benzene-insolubleglass-like styrene co-polymers small-amounts of esters of levulinic acidpossess flow at molding temperatures, and when plasticized in relativelylarge proportions'are tough rubbery products. The new plasticizingagents not only do not impair the strength characteristics, clearness,and transparency of the unplasticized insoluble co-polymers, but in manycases cause improved strength characteristics and a decreased tendencyto blush or craze upon aging.

The esters of levulinic acid which we have found to be most suitable asplasticizing agents for the benzene-insoluble glass-like co-polymers ofstyrene may be represented bythe following formula CHa-CO-CHz-CEIa-COO-Rwherein 'R represents an organic radical, e.- g. alkyl, alkenyl, aryl,aralkyhcycloalkyl, aryloxyalkyl, halo-alky l, halo-aryloxy-ailryl, etc.Examples of such compounds are allyl levulinate, 2-cl'1loroa1lyllevulinate, cyclohexyl levulinate,

'benzyl levulinate, betaiphenoxyl-ethyl levulinate,beta-(4-tertiarybutyl-phenoxy) ethyl levulinate, betas(3-chloroz-xenoxy)-ethyl levulinate, etc.

The new plastic compositions comprising benzene-insoluble glass=likeco-polymers of styrene and esters of levulinic acid are preferablyprepared by polymerizing a mixture of styrene and the co-polymerizingagent in the presence of the plasticizing agent. The latter may beemployed in any proportion within the limits of its compatibility withthe co-polymer, but is usually employed in an amount representing from0.5 to 50 per cent by weight of the entire composition, the mostefiective amount depending somewhat upon the use to which thecomposition is to be put. For example, compositions which can beadequate plasticity and per cent by weight of the plasticizing agent,

whereas rubber-like compositions contain a somewhat greater proportionof plasticizing agent, e. g. 35'to'50 percent. Co-polymerizing agentsare usually employed in amounts representing 0.1 to per cent by weightof the styrene, although the optimum amount depends upon the particularco-polymerizing agent employed and upon the properties desired in thecomposition. Polymerization is usually carried out by heating themixture of monomeric styrene, co-polymerizing agent, and plasticizingagent .at a moderately elevated temperature, e. g. 60-180 0., for /z to14 days, during which time the mixture gradually polymerizes to form aresinous polymer having the plasticizing agent homogeneously dispersedtherethrough.

Compositions comprising benzene-insoluble copolymers of styrene of thetype capable of being swelled by solvents may be prepared by forming theco-polymers in the absence of plasticizing agent, that is, bypolymerizing a mixture of monomeric styrene and a co-polymerizing agent,and thereafter causing the insoluble co-polymers to swell to a gel in asolution of the plasticizing agent and a swelling solvent, e. g.benzene, toluene, carbon tetrachloride, etc. During the swellingoperation the plasticizlng agent'is absorbed by the co-polymer gel, andafter the removal of solvent the co-polymer is recovered in a. formhaving the plasticizing agent uniformly and intimately dispersedtherethrough. This method of incorporating a plasticizing agent with astyrene co-polymer forms the subject matter of a co-pending applicationof Britton and Marshall, Serial No. 209,736, filed May 24, 1938. A thirdmethod which may be employed in preparing the new compositions comprisesmechanically mixing the finely-divided co-polymer with a plasticizingagent in a Banbury-type mixer or on,

heated compounding rolls until a homogeneous composition is obtained.

The following examples illustrate a number of ways in which theprinciple of the invention has been applied but are not to be construedas limiting the same:

EXAMPLE 1 Compositions comprising benzene-insoluble glass-likeco-polymers of styrene and dioxylene dicinnamate .plasticizedmwithvarious esters of levulinic acid were prepared by polymerizing mixturescontaining 50 grams of monomeric styrene, 0.25 gram of dioxylenedicinnamate, and from 1 to 4.5 grams of the plasticizing agent at atemperature of 100 C, for 336 hours. The

resulting co-poiymers were ground, dried, and molded into testspecimens, employing a molding temperature of 160 C. No diiiiculty wasexperienced in the molding and-no significant impairment of impactstrength and tensile strength occurred. The data obtained is summarizedin the following table, which for purposes of comparison includes dataon an unplasticized benzene-insoluble co-polymer prepared under the Amixture of 25 grams of styrene, 2.5 grams of diallyl maleate, and 20grams of cyclohexyl levulinate was polymerized at C. for 12 hours. Theresulting co-polymer was ground, dried, and

, molded at C. The molded product was clear,

colorless, and rubbery.

We claim: 1. A rubbery composition of matter comprising abenzene-insoluble glass-like co-polymer of styrene and, as a plasticizertherefor, between about 35 and about 50 per cent by weight of a compoundof the formula wherein R represents an aryloxy-alkyl radical.

2. A rubbery composition of matter comprising a benzene-insolubleglass-like co-polymer of styrene and, as a plasticizer therefor, betweenabout I 35 and about 50 per cent by weight of beta-(3- chloro-2 -xenoxy)-ethyl levulinate.

32 A rubbery composition of matter comprising a benzene-insolubleglass-like co-poiymerof sty-

